The proposed research develops appropriate methods for path analysis of quantitative traits in nuclear families, incorporating specific maternal effects with extensions to cover pedigree structures. This would enable tests for maternal effects, assortative mating and basic hypotheses on genetic and environmental effects. These methods will be applied to lipoprotein concentrations, IgE levels and periodontal disease and blood pressure. We also propose to develop a separate theory of path analysis for prevalence data on semi-continuous traits with applications to schizophrenia, cleft lip and palate; this will be developed through conditional probabilities and polychoric functions.